1. Field of the Invention
The invention relates to an apparatus for implementing water separation in the vacuum system of a paper machine. Furthermore, the invention relates to a method for implementing water separation in the vacuum system of a paper machine.
2. Description of Background Art
It is generally known to use vacuum for dewatering a web at the upstream end of a paper/cellulose/cardboard-making machine. The removed water must be separated from the vacuum flow prior to passing the air to a vacuum pump or blower. To this end, a steel tank has conventionally been employed wherein the flow is retarded and water is separated from air utilizing a cyclone concept. For greater air flow volumes concrete tanks have been developed in which separation of water occurs by retarding the flow velocity and then passing the air-water aerosol via droplet separation lamella plates. In the appended drawing (FIG. 1) is shown a typical concrete separation tank embodiment; this kind of construction is used by, e.g., in the structure disclosed in 1985 by the Sulzer Escher Wyss company.
In the state of the art, this construction is employed in conjunction with vacuum systems equipped with turbo blowers. In practice the system is relatively functional, but needs a lot of maintenance by the operator. A particular problem arises from the adherence of pulp to the walls of the tank structure as well as to the droplet separation lamella plates. The separation efficacy is substantially deteriorated when the lamella plates gather a layer of pulp. Resultingly, fiber can pass along with the air flow to the vacuum pump/blower. In turbo blowers the pulp fibers cling to the blade wheel that may thus become unbalanced. Pulp also adheres to the flow passageways of the blower thereby causing loss of vacuum efficacy. Moreover, in certain blower constructions pulp has penetrated into the labyrinth seals between the blade wheels thus causing damage in the blower.
It must further be noted that the prior-art construction has lamella plates located in the center of the separation tank. During system maintenance the operating personnel thereof must have access to the space behind the lamella plates for cleaning the entire tank. The lamella plate compartment must be provided with a door that can be opened during a maintenance shutdown. Cleaning the lamella plates is an extremely lengthy process and, moreover, they are expensive to fabricate.
Another disadvantage is that in practice a long piping must used to connect this kind of concrete separator tank to the blowers. As the vacuum flow takes place at 100% RH and air is cooled in the long piping, condensation occurs. Subsequently, the condensed water causes erosion in the blade wheels of the blower. These problems need be overcome.